Galina Voskoboeva of Kazakhstan returns a shot to Serena Williams of the United States during their second round women's singles match on Day Four of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 29, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Yaroslava Shvedova, of Kazakhstan, returns a shot to Serena Williams during a third round match at the U.S. Open tennis tournament early Saturday, Aug. 31, 2013, in New York. (Photo: AP)

Kristina Mladenovic, of France, returns a shot to Jamie Hampton during a second round match at the U.S. Open tennis tournament Thursday, Aug. 29, 2013, in New York. (Photo: AP)

Urszula Radwanska of Poland returns a backhand to Sloane Stephens of the U.S. at the U.S. Open tennis championships in New York, August 28, 2013. (Photo: Reuters)

Angelique Kerber of Germany celebrates a point during her women's singles third round match against Kaia Kanepi of Estonia on Day Five of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 30, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Anna Schmiedlova of Slovakia plays a forehand against Stefanie Voegele of Switzerland during their first round match on Day One of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 26, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Eugenie Bouchard of Canada returns a shot to Angelique Kerber of Germany during their 2013 US Open women's singles match at the USTA Billie Jean King National Tennis Center August 29, 2013 in New York. (Photo: AFP)

Anastasia Pavlyuchenkova of Russia returns a shot during her women's singles third round match against Agnieszka Radwanska of Poland on Day Five of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 30, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Paula Ormaechea, of Argentina, returns a shot to Sabine Lisicki, of Germany, during the second round of the 2013 U.S. Open tennis tournament, Thursday, Aug. 29, 2013, in New York. (Photo: AP)

Vera Dushevina of Russia returns a shot against Sabine Lisicki of Germany during their first round women's singles match on Day One of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 26, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Monica Puig of Puerto Rico returns to Alisa Kleybanova during their US Open 2013 women's singles match at the USTA Billie Jean King National Center August 26, 2013 in New York. (Photo: AFP)

Sorana Cirstea of Romania returns the ball to Kurumi Nara of Japan during their US Open 2013 women's singles match at the USTA Billie Jean King National Center August 29, 2013 in New York. (Photo: AFP)

Caroline Garcia of France plays a forehand during her women's singles second round match against Laura Robson of Great Britain on Day Three of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 28, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Camila Giorgi, of Italy, serves to Caroline Wozniacki, of Denmark, during the third round of the 2013 U.S. Open tennis tournament, Saturday, Aug. 31, 2013, in New York. (Photo: AP)

Michelle Larcher De Brito of Portugal hits a return to Maria Kirilenko of Russia at the U.S. Open tennis championships in New York August 29, 2013. (Photo: Reuters)

Heather Watson of Great Britain returns a shot to Simona Halep of Romania during their women's singles first round match on Day Two of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 27, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Shuai Peng of China returns a shot during her women's singles second round match against Svetlana Kuznetsova of Russia on Day Four of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 29, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Bojana Jovanovski, of Serbia, returns a shot to Petra Kvitova, of Czech Republic, during the second round of the 2013 U.S. Open tennis tournament, Thursday, Aug. 29, 2013, in New York. (Photo: AP)

Alison Riske of the United States returns a shot during her women's singles fourth round match against Daniela Hantuchova of Slovakia on Day Eight of the 2013 US Open at USTA Billie Jean King National Tennis Center on September 2, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Victoria Duval of the United States of America plays a forehand during her women's singles second round match against Daniela Hantuchova of Slovakia on Day Four of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 29, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Alexandra Dulgheru of Romania serves to Ana Ivanovic of Serbia during their second round women's singles match on Day Four of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 29, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Julia Goerges, of Germany, returns a shot to Christina McHale at the 2013 U.S. Open tennis tournament Tuesday, Aug. 27, 2013, in New York. (Photo: AP)

Elina Svitolina of Ukraine serves to Christina McHale of the United States during their second round women's singles match on Day Four of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 29, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)

Galina Voskoboeva

Galina Voskoboeva of Kazakhstan returns a shot to Serena Williams of the United States during their second round women's singles match on Day Four of the 2013 US Open at USTA Billie Jean King National Tennis Center on August 29, 2013 in the Flushing neighborhood of the Queens borough of New York City. (Photo: Getty Images)